Dennis "Slick" Lilly put on a prison guard's uniform and walked out of jail in December 1986, and that's the last the cops ever saw him alive. Despite being on the FBI's list of Most Wanted Criminals, Lilly was so slick that he disappeared into the life of a law-abiding small businessman in a woodsy town near Seattle.

Dennis Lilly died of cancer at the age of 64, more than a quarter century after he walked out of a Missouri state prison dressed as a jail guard. Fearing an official burial would give away the secret, his wife of many decades simply buried him behind their house in Gold Bar, Washington.

They took new names—David and Amanda Murray—and they did honest work in their adopted hometown, running a mail shop in the nearby town of Monroe, across from the Jack in the Box on Highway 2.

"We're open later than the U.S. Post Office in Monroe," their small business website says. And unlike the post office, the Lillys' mail shop didn't have to display those Most Wanted Fugitives posters from the FBI.

Dennis Lilly's mugshot was regularly featured on those FBI posters, as well as on the television series America's Most Wanted.

Their lives were quiet, according to the Sky Valley Chronicle, and their business was hardly hidden from view. Dennis volunteered as a community Santa Claus at Christmastime. A daughter was born and is now an adult.

The Lillys, who married when Dennis was still in prison for burglary and assault, eventually had the same mundane domestic problems so many people have. He left for California, his wife's home state, but he came back to Gold Bar when he was sick with pancreatic cancer. That's where he died, with his family, in 2012.

Had his wife not tried to set up a retirement brokerage account, she might've taken the secret to her grave, too. But the Social Security number she had used for decades didn't match up with the birthdate she gave, and some office worker at a financial services conglomerate decided to call the FBI.

When the Feds showed up at Amanda Murray's house and told her they knew she was really Mary Lilly, wife of an infamous fugitive, she reportedly confessed that she buried her husband out back.